Tech Myth 2: A battery should be at zero before you recharge it
The idea that you should always completely discharge a battery before charging it up again has legitimate origins, but it doesn’t apply to current technology. Years ago, when nickel–metal hydride (NiMH) and nickel-cadmium (NiCad) batteries were common, they suffered from an issue called “battery memory”: Unless the battery was completely spent before being recharged, it would “remember” how much power it had used and only charge back up that amount. If done repeatedly over time, the battery would never charge totally again.
Fortunately, the lithium-ion (Li-ion) battery that’s probably in your phone or laptop right now doesn’t suffer from this issue, at least not in any significant way. In fact, with Li-ion batteries, you can actually do more harm than good by letting them die before charging them again, because they have a limited number of charge “cycles” (meaning times you can completely discharge and recharge them) before batteries start to hold less overall power.
Luckily, according to Battery University, the solution is pretty simple: Charge your devices from time to time before they fully die. These so-called shallow discharges mean you don’t use a full charge cycle every time you top off your phone after carrying it for a few hours or plug in your laptop after working on the couch for the afternoon. In reality, the biggest enemy of modern batteries is temperature. The cooler you can keep your battery, either while charging it or while it’s in use, the more you can prolong its life.